i made some changes to a file a month ago. i just realized today that they didn't go anywhere; the GitHub web-site has no history of my changes.

The client has no indication that anything is out of date (there are no "uncommitted changes"). But there are "unsynced commits":

How do i sync unsynced commits?

I tried nothing, and i'm fresh out of ideas

i tried clicking the sync button (whatever that means), but all i get (after a progress bar moves for about 7 seconds) is:

failed to sync branch
You might need to open a shell and debug the state of this repo.

Clicking OPEN SHELL, causes a powershell prompt to appear, where i type:

debug the state of this repo

But that doesn't seem to do it:

How do i sync unsynced commits in the GitHub for Windows client?

解决办法：

fatal: Not a git repository (or any of the parent directories): .git

提示说没有.git这样一个目录，解决办法如下：

git init就可以了！